/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.sdk.extensions.euphoria.core.client.util;



import com.bff.gaia.unified.sdk.extensions.euphoria.core.annotation.audience.Audience;

import com.bff.gaia.unified.sdk.extensions.euphoria.core.client.functional.CombinableReduceFunction;

import com.bff.gaia.unified.sdk.extensions.euphoria.core.client.functional.UnaryFunction;



import java.util.Comparator;



/** Calculate maximum. */

@Audience(Audience.Type.CLIENT)

public class Max {



  private Max() {}



  /**

   * Return {@code CombinableReduceFunction} to calculate maximum of input.

   *

   * @param <InputT> the type of elements handled

   * @param <X> the type of key by which to compare the elements

   * @param extract the key extraction function

   * @return a combiner function which delivers the "maximum" element seen; never {@code null}

   */

  public static <InputT, X extends Comparable<X>> CombinableReduceFunction<InputT> of(

      UnaryFunction<InputT, X> extract) {



    return values ->

        values

            .max(Comparator.comparing(extract::apply))

            .orElseThrow(() -> new IllegalStateException("Got empty stream on input!"));

  }

}